Founding of al-Fusṭāṭ

After the fortress of Babylon fell to ʿAmr ibn al-ʿĀṣ's army, the caliph ʿUmar refused a capital across the water at Alexandria — no river, he insisted, should lie between him and his army. So the camp by the fortress became a city: al-Fusṭāṭ, "the tent," laid out around ʿAmr's mosque, the first in Africa.

The garrison town grew into Egypt's administrative heart and, layer by layer — al-ʿAskar, al-Qaṭāʾiʿ, then the Fatimids' al-Qāhirah beside it — into the megacity that still keeps ʿAmr's mosque at its oldest corner.

The founding is dated by year only, 21 AH in the common reckoning, and the entry keeps that precision.